1. Field of the Invention
The present invention relates to multi-processor apparatus. A multi-processor apparatus includes a plurality of processors for processing digital data and is especially suitable for use in processing digital image signals. Two or more processors can operate on data at the same time, thereby increasing data throughput.
2. Description Relative to the Prior Art
Where large amounts of digital data need to be processed, a multi-processor apparatus is often suitable for use. One particular application where multi-processor apparatus is used is in digital image processing. Digital image processing is used to perform image enhancement processing on a digital image to produce an enhanced digital image. This enhanced digital image is read out from memory and provided to a high speed "scan" printer. Large amounts of data must be processed. In order to increase the throughput rate, multi-processor apparatus having an array of processors is used. These processors are often microcomputers. Because of the amount of data involved and the need for increased throughput, the use of multi-processor apparatus is becoming more frequent.
A typical prior art multi-processor apparatus architecture is shown in FIG. 1. It operates by sharing a single bus between processors and a single large main memory (data memory). Each processor makes a request to gain control of the bus when it needs access to a location in the main memory. During each data transaction all other processors which are not busy processing data must wait for the bus to again become free. An arbitor circuit (not shown) establishes the order in which the processors can gain access to the bus. Throughput (data transfer rate) increases as the number of processors is increased. This increase in throughput continues only up to a point. Thereafter, an increase in the number of processors actually decreases the throughput.